* This number is not really the number of browsers detected. All
browsers (known and unknown) can be detected by products that support
user agent listing (AWStats,Analog,Webalizer,Sawmill). The 'browser
detection feature' and number is the number of known browsers for which
different versions/ids of same browser are grouped by default in one
browser name.

** AWStats can detect robots visits: All robots among the most common
are detected, list is in robotslist.txt
(250Kb). Products that are not able to do this give you false
information, above all if your site has few visitors. For example, if
you're site was submitted to all famous search engines, robots can make
500 visits a month, to find updates or to see if your site is still
online. So, if you have only 2000 visits a month, products with no
robot detection capabilities will report 2500 visits (A 25% error !).
AWStats will report 500 visits from robots and 2000 visits from human
visitors.Sawmill Analytics uses a "currently active" list of robots
based on the robotstxt.org database.

*** AWStats has url syntax rules for the most popular search engines
(that's the 'number detected'). Those rules are updated with AWStats
updates. But AWStats has also an algorithm to detect keywords of
unknown search engines with unknown url syntax rules. Sawmill uses
unique syntax to detect 67 search engines, and you can add any number
of custom SE's.

**** Most log analyzers have poor (or not at all) robots, search
engines, os or browsers detection capabilities and less features (no or
poor visits count, no filter rules, etc...).
It is not possible to add all AWStats features to other log analyzers,
so don't forget that benchmarks results are for 'different features'.
For this benchmark, I did just complete Webalizer and Analog robots or
search engines databases with part of AWStats database. So Webalizer
config file was completed with this file,
Analog config file was completed with this file.
Note that without this very light add (using default conf file),
Webalizer speed is 3 times faster, Analog is 15% faster).
Benchmark was made on a combined (XLF/CLF) log record on an Athlon 1GHz.
You must keep in mind that all this times are without reverse DNS
lookup. DNS lookup speed depends on your system, network and Internet
but not on the log analyzer you use. For this reason, DNS lookup is
disabled in all log analyzer benchmarks. Don't forget that DNS lookup
is 95% (even with a lookup cache) of the time used by a log analyzer,
so if your host is not already resolved in log file and DNS lookup is
enable, the total time of the process will be nearly the same whatever
is the speed of the log analyzer.

***** Some visitors
use a lot of proxy servers to surf (ie: AOL users), this means it's
possible that several hosts (with several IP addresses) are used to
reach your site for only one visitor (ie: one proxy server download the
page and 2 other servers download all images). Because of this, if
stats of unique visitors are made on "Hits", 3 users are reported but
it's wrong. So AWStats, considers only HTML pages to count unique
visitors. This decrease the error (not totally, because
it's always possible that a proxy server download one HTML frame and
another one download another frame).
Sawmill Analytics allows you to choose what you define as a visitor -
by default the client IP is used, but you can use a cookie (persistant
or session) or any custom string, or combination of string from teh log
data.

(a) Data were provided by Sawmill company (Graham Smith).

(b) With such log format, there is no user agent information in log
file, so some reports are broken. For example, it's not possible to
make reports on browser or os for (information is not stored in log
file). To solve this, use another log format (like the combined
format).